During cataract surgery, the human lens is removed from within the lens capsule and replaced by an artificial lens. This is performed by opening a small hole in the anterior capsule (a capsulorhexis) and then destroying and removing the human lens by phacoemulsification. However, lens cortex and epithelial cells remain following the lens removal, and irrigation/aspiration is routinely used to remove the visible cortex remnants. It is unreasonable to expect all lens epithelial cells (LECs) which are bound to both the anterior and posterior capsule to be removed by this method.
LECs which remain within the capsule have been shown to mutate and grow over the posterior surface of the implanted intra-ocular lens (IOL) thus causing posterior capsule opacification (PCO). This complication of cataract surgery has historically occurred at a rate as high as 30% however recent IOL designs have reduced this to around 2-5% at 2 years. It remains unclear what the longer term rates of PCO with these IOLs will be.
The current treatment for PCO is a Posterior Capsulotomy using a Yag laser. Although the complication associated with this procedure is small, the cost is significant and there is a risk of retinal detachment.
Current methods for reducing the rate of PCO include IOL design. It has been shown that a lens with sharp edges causes a barrier to LEC growth. However, lens capsule fibrosis occurs and these IOLs have been shown to cause vision problems particularly at night due to reflections from these edges.
It has been proposed that cytotoxic chemicals can be used to destroy these epithelial cells, however, there is a risk that these chemicals damage other intranuclear structures.
Research is currently underway into using accommodating IOLs, and clear lens extraction for the correction of refractive errors. However, for these technologies to be successful chronically, the lens capsule must remain flexible and free of fibrosis.
Therefore, there is still a need for a device which overcomes the current problems associated with adequate capsule cleaning and LEC removal.